One of the major breakthroughs of the Wright brothers was the ability
to control and maneuver their
aircraft.
Since we live in a three dimensional world, it is necessary to control
the attitude, or orientation, of a flying aircraft in all three
dimensions.
The first aircraft to achieve complete active control was the
1902 glider
which is shown on this slide.
In flight, any aircraft will rotate about its
center of gravity,
a point which is the average location of the mass of the aircraft.
We can define a three dimensional coordinate system through the
center of gravity with each axis of this coordinate system perpendicular
to the other two axes.
We can then define the orientation of the aircraft by the amount of
rotation of the parts of the aircraft along these principal axes.

The yaw axis is defined to be perpendicular to the plane of the
wings. A
yaw motion
is a movement of the nose of the aircraft from side to side.
The pitch axis is perpendicular to the yaw axis and lies in the
plane of the wings. A
pitch motion
is an up or down movement of the nose of the aircraft.
The roll axis is perpendicular to the other two axes and lies
in the fuselage of the aircraft pointing towards the nose. A
rolling motion
is an up and down movement of the wing tips of the aircraft.

During the flights of
1900 the Wrights tested a
method called
wing warping
to achieve roll control. Through a series of cables, the Wrights could twist
the wing tips up or down relative to the rest of the wing. This produced an
unbalanced force on the wing which caused the aircraft to roll.
Modern airliners and fighter planes, however,
no longer use wing warping for roll control. They typically use either
ailerons or
spoilers
which are moving sections on the wing of the aircraft.
When you travel on an airliner, watch
the wings during turns. The pilot rolls the aircraft in the direction
of the turn. You will probably be surprised at how little deflection
is necessary to bank (roll) a large airliner. You can
tell whether an airliner is using spoilers or ailerons by noticing
where the moving part is located. At the trailing edge, it's an
aileron; between the leading and trailing edges, it's a spoiler.

During the flights of
1901 the Wrights included a movable
elevator
at the front of the aircraft to control pitch.
The placement of the elevators at the front of
aircraft is rather unique for the Wright aircraft. Modern
aircraft
typically have the elevator
at the rear, attached to the horizontal
stabilizer.
The elevator is used at take off to rotate the aircraft and get the
nose pointed up as you leave the runway.

The movable
rudder
was added to the
1902
aircraft to provide yaw control. They found it
necessary to keep the nose pointed in the direction of a turn to
avoid adverse yaw which they first encountered with the
tailless 1901 glider.
The Wright's used flat plate airfoils for their rudders and deflected the
entire surface from side to side.
On modern aircraft, the rudder is a
separate piece attached to the vertical
stabilizer. The combination creates a
symmetric airfoil
and produces no lift when the rudder is aligned with the
stabilizer. Forces to the left or right then depend on the
deflection of the rudder. Modern fighter planes sometimes have two vertical
stabilizers and rudders because of the need to control the plane with
multiple, very powerful engines.